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TE79-4000CPA/939 – Textron Aviation OEM Cabin Pressure Test Adapter
Available now on the Airparts.aero Marketplace.
The Textron Aviation TE79-4000CPA/939 is a specialized, OEM-certified ground support equipment (GSE) adapter designed for the rigorous testing of aircraft cabin pressurization systems. This component serves as the critical interface between the aircraft's fuselage pressure ports and an external Cabin Pressure Test Set. Specifically engineered for the Beechcraft King Air and Cessna Citation series, the TE79-4000CPA/939 allows maintenance technicians to perform controlled pressure and leak-down tests while the aircraft is stationary on the hangar floor, ensuring the integrity of the pressure vessel and the accuracy of cockpit pressure instrumentation.
Fabricated from high-strength aerospace alloys with precision-machined threads, this adapter is designed to provide a gas-tight seal under high differential pressures ($P_d$). The "939" configuration is often associated with specific airframe model effectivity, featuring unique fitting geometries that prevent the use of incorrect adapters on sensitive static or pitot lines. For the avionics or airframe technician, this tool is indispensable for verifying that the cabin altitude controllers, outflow valves, and safety valves are functioning within the narrow margins required for high-altitude flight safety.
Key Features
Precision-Engineered Seal: Features high-grade elastomer O-rings and seats designed to prevent "phantom leaks" that could lead to false-negative results during a pressure vessel decay test.
Model-Specific Geometry: The adapter is keyed or sized specifically for Textron airframes, preventing mechanical damage to the fuselage skin or the internal pressure-sensing lines.
High-Pressure Resilience: Rated to withstand the maximum relief valve pressures of business jets and turboprops, ensuring technician safety during maximum-differential ($P_d$) tests.
Anodized Durability: Finished with a hard-coat anodization to resist corrosion from hangar chemicals and to prevent surface marring when handled by heavy-duty GSE hoses.
Integrated Safety Vents: Designed with bleed-off capabilities to ensure that pressure can be safely neutralized before the adapter is disconnected from the aircraft.
Technical Specifications
Part Number: TE79-4000CPA/939
Manufacturer: Textron Aviation OEM (Cessna / Beechcraft)
Component Type: Cabin Pressure Test Adapter / Fitting
Connection Type: Quick-disconnect or threaded (model dependent)
Material: 6061-T6 Aluminum or Stainless Steel
Finish: Blue or Red Anodized (standard for GSE identification)
Operating Limit: Typically rated up to 15.0 PSID
Governing Standards: SAE AS4059 (GSE requirements)
Certification: OEM Original Equipment / Tooling
Aircraft Compatibility
Beechcraft King Air Series: 90, 200, 300, and 350 models.
Cessna Citation Series: 525 (M2/CJ), 560 (Excel/XLS), and 680 (Sovereign).
Beechcraft 1900D: Regional transport configurations.
Note: The TE79-4000CPA/939 is a serial-number-specific tool. Always refer to the Model-Specific Maintenance Manual (Chapter 05/21) or the Tooling Catalog to verify this is the correct adapter for your aircraft’s pressure ports.
Applications
Annual/Phase Inspections: Mandatory leak-down testing of the fuselage pressure vessel.
Troubleshooting: Identifying "hiss" points or failed seals around windows, doors, and control surface cable penetrations.
Instrumentation Calibration: Verifying the accuracy of the cabin altimeter and rate-of-climb indicators against a calibrated external source.
Why Choose TE79-4000CPA/939?
In the world of cabin pressurization, the "leak-down rate" is the primary metric for airworthiness. Utilizing non-OEM adapters or "shop-made" fittings can result in damage to the aircraft’s Static Ports or Outflow Valve sensing lines, leading to catastrophic instrumentation failure in flight. The TE79-4000CPA/939 is built to the exact tolerance of the aircraft's fuselage fittings, ensuring that the test results are accurate and that the aircraft's pressure vessel remains undamaged. For Part 145 repair stations, using OEM-certified tooling is a critical requirement for maintaining compliance with Textron service standards.
Note: The TE79-4000CPA/939 is a specialized maintenance tool. Pressure testing involves significant stored energy; technicians must adhere strictly to the safety precautions in AMM Chapter 21. Personnel should never remain in the aircraft during a high-differential pressure test unless specifically required by the procedure. Ensure all safety valves and "remove before flight" plugs are correctly configured before applying pressure.
